Electric control system



Feb. 27, 1934. R. J. STEVENS 1,948,685

mac-mm CONTROL SYSTEM Filed July :5, 1931 3 Shets-Sheet 1 WITNESSESZINVENTOR 3 FOfid/d cl Szeuefls ATT Feb. 27, 1934.

WITNESSES:

R. J. STEVENS 1,948,685

ELECTRIC CONTROL SYSTEM Filed July 5. 1931 3 Sheets-Sheet 2 INVENTOR 5770/0 JSzeuens.

Feb. 27, 1934. R. J. STEVENS ELECTRIC CONTROL SYSTEM Filed July 3, 19313 Sheets-Sheet 3 INVENTOR Rona Id J Sfevens ATT RNEY Patented Feb. 27,1934 ELECTRIC CONTROL SYSTEH Ronald John Stevens, New Malden,

Application July 3, 1 931, Serial No. 518,573 In Great Britain July 7,1930 11 Claims. (Cl. 112-152) This invention relates to control orsignalling systems for objects movable in a definite path, as forexample, lifts, elevators, railway cars, and like vehicles, andparticularly to such systems of the character in which are employedrelays operated by a relatively moving magnetizable member for eifectingcontrolling or signalling operations in accordance with variations inthe displacement of the relatively movable objects.v

the lift shaft respectively, the relay device being equipped with meansfor maintaining an electric or magnetic field of force in its vicinityand adapted to be rendered operative to effect a desired signal orcontrol operation by the passage of the magnetizable member through saidfield.

The present invention .provides a control or signalling system of theabove-mentioned character in which the relay device comprises aninductance, preferably in the form of a transformer, the magneticreluctance of the core of which can be varied by a magnetizable memberor shield formed with a specific graduated profile and the progressivevariation of the magnetic reluctance, with the corresponding variationin the voltage in one winding of the transformer for example, during therelative movement of said inductance or transformer and said profiledmember, is utilized to cause the continuous variation of the conditionof associated control or signalling apparatus or to effect a pluralityof specific operations of associated control or signalling apparatus ina predetermined sequence.

Conveniently, the transformer is constructed with an air gap into whichthe profiled magnetizable member, hereinafter referred to simply asshield, is adapted to extend by varying amounts during relative movementof the objects with which said transformer 'and said shield are adaptedto be operatively associated.

The transformer may be equipped with two or more windings arranged sothat the mutual inductance between the windings or pairs of windings isa maximum when the amount of .the shield extending into the air gap is aminimum, so that by increasing or reducing the amount of the shield inthe air gap the voltage across a secondary winding of the transformer iscorrespondingly varied. Alternatively, the transformer may be soarranged that the windings thereof are substantially mutuallynoninductive when the magnetizable member does not extend within the airgap, the mutual inductance between said windings being varied as theamount of the member projecting into the air gap varies thereby to causecorresponding changes in the voltage across the secondary winding.

In applying the invention by way of example to the control of anelectrically operated lift or elevator, the transformer may be mountedon the lift car so that the cores project horizontally away from theside wall of the car, the primary winding or windings of the transformerbeing adapted to be connected to a source of alternating currentpreferably of ordinary commercial supply frequency.

The shield may comprise an iron strip which 70 is vertically mounted inthe lift shaft in longitudinal alignment with the air gap of thetransformer. The strip being inclined or bowed so that during movementof the transformer relatively to the strip, the amount of the latterwhich 7 projects into the air gap increases progressively to a maximumand then preferably progressively decreases. I

Alternatively and preferably the shield and the inductance ortransformer are not disposed in the lift shaft or on the lift, but arelocated in a control room, the inductance or transformer beingconveniently fixed in position whilst the profiled magnetizable memberor shield, which may be of relative small dimensions, is eithergear-driven from the lift or is adaptedto be clutched to some otherrotating or moving member or is moved by electric means during suchtimes that continuous acceleration and deceleration are required.

According to an important feature of the invention the one or moresecondary windings are connected to the input side of a thermionic valveamplifier, the output circuit of which includes the field winding of thegenerator of the Ward-Leonard motor-generator set employed for haulingthe lift or elevator. Usually it will be found more convenient to employan auxiliary or pilot amplifier exciter generator to supply the field ofthe Ward-Leonard generator and itself excited by ator, of theWard-Leonard system, is serially included, as well as the exciter-fieldwinding. in the anode circuit of the output valve of the thermionicamplifiertotheinputofwhiehthesecondary of the variably shieldedtransformer is connected as hereinbefore set forth, the arrangementbeing suchthatasthe shieldingisreducedthe increasing exciter voltage dueto the increue in anode current flowing in the exciter field is added,so to speak, to the usual anode potential of the output valve. This initself is advantageous in several respects. Thus the usual anode supplycan be obtained from ordinary supply mains'or other convenient sourcesuch as an auxiliary generator for supplying brakes and other controlgear at, say 200 volts, and the pilot exciter generator convenientlygenerates at a similar voltage on full excitation, so that at startingthe anode voltage is 200 whilst at full speed it is 400, which is aconvenient value for giving an anode current of say 12 to 15 watts whichis suitable for the field excitation of the pilot generator. Furthermoresuch increase in anode volts with speed has an important effect incompensating for speed-load drop since the valve is operating on theresulting steepened characteristic which counteracts the effect of thefield of the main generator becoming partially and increasinglysaturated with increase in load.

If now the pilot generator has added to it a small additive series fieldwinding excited in accordance with the main motor current a furthercumulative effect can be obtained, according to a further feature of theinvention, in compensating for the speed-load drop, whereby the correctlanding speed can be obtained irrespective of the load since the mainand pilot generators are relatively unsaturated at such slow reducedspeed. Such series winding being small will not give rise toirregularities or delay in changes in the field of the pilot generator.The voltage in such auxiliary field winding is moreover added to theanode voltage of the valve thus producing a still further increasedcurrent in the desired sense in the shunt field of the pilot generator.

It will be appreciated that if a valve of the amplifier fails the liftor other moving object will automatically be brought to rest by reasonof the voltage on the field winding failing. It will also be appreciatedthat the amplifier can be omitted if the alternating current in theshielded winding of the transformer is made sufficiently strong tooperate, after being passed through a rectifier, the field winding orother controlled apparatus direct.

In lift or elevator practice it is particularly desirable that thecontrolling apparatus should be capable of producing accurate stoppageof the lift or elevator at a fioor or landing. For this purpose theprofile shield may be provided at its effective center portion with apronounced projection or hump which may be of rectangular shape, so thatwhen the lift has been progressively decelerated as above set forth, itmay be stopped through the operation of one or more suitableelectrically controlled or contactor switches consequent upon theintroduction of a relatively large amount of iron at the hump into theair gap.

In the preferred arrangement however the lift is decelerated through theagency of the aforesaid profiled shield to a steady minimum andrelatively slow speed just before the car reaches the selected fioor,and when the car, thustravelofcamswitchesorinductorrelayslocatedappropthtelyintheliftshaft,butpreferablybymeam of a ustem of "pick-up winding andcontrolling electromagnet or inducer, similar means beim also preferablyemployed to initiate automatically at the correct moment thedeceleration of the liftaothatitshalltravelattheslowspeedwhen closelyapproaching the selected floor or landing as above mentioned.

A preferred embodiment of the invention as applied to lift control isbriefly as follows. The profiled shield is of disc form with a spiral orapproximately spiral periphery or profile and is rotatably mounted androtated by an electric motor which is adapted, when required, normallyto run at constant speed. and which, in the arrangements hereinafter setforth, is adapted to be reversed so that the shield produces thedeceleration and is returned to the innermost or starting" position inreadiness for producing an acceleration or deceleration of the liftagain.

Two spiral discs or other shields are conveniently provided, namely, onefor producing acceleration and the other for producing deceleration, theeffect of one of them being precluded according to which kind of changeof speed is required at any time. The shield motor is adapted to bestarted such as by means of a controller or press button on the lift orlanding and to be reversed and finally stopped by cam switches orinductor relays or pick-up coil and inducer windings as hereinbeforebriefly set forth and as hereinafter more fully described.

Thus, when the lift is required to pass floors or landings the shieldmotor may be started by hand operations of the car controller or of apress-button and the lift motor automatically accelerated up to fullspeed, whereupon the shield motor is automatically stopped, such as bymeans of a switch operated by a cam associated with the acceleratingshield, the lift motor continuing to run at its maximum speed untildeceleration is required as the lift approaches the selected floor. Itwill be appreciated that the acceleration can thus always be thepermissible maximum. When the lift traveling at full speed arrives at acertain predetermined distance from the selected floor or landing theshield motor is automatically reversed to cause the lift to bedecelerated to a minimum speed just before it reaches said fioor orlanding whereby the maximum permissible rate of deceleration can bealways obtained. The lift traveling at the minimum speed can then bestopped exactly at the fioor, preferably by the selectively energizedcontrolling electro-magnet or inducer which excites the pick-up coil andthereby effects the deenergization of all necessary control circuits andmain circuits so that the lift is held stationary at the fioor.

When, however, floor to fioor travel of the lift is only required itwill usually not be possible to accelerate the lift to the maximum speedbefore deceleration is again required, but under such circumstances themaximum permissible rates of both acceleration and deceleration canstill be obtained by means of the retarding inducer and the pick-upwinding arranged to cause the shield motor to reverse when the lift is apredetermined distance from the floor, less than required for fullspeed, no matter what the actual speed may be at the particular momentwhen deceleration is required to bring the lift to rest at the fioor.Thus the rate of deceleration may be the same, or substantially thesame, although the distance in which the lift decelerates to the flooris less than in the case where the lift is traveling at full speed. Suchadditional inducer is located in the lift shaft adjacent the floor butintermediate between the stopping inducer and the inducer whichinitiates deceleration from full speed. Such two retarding inducers aswell as the stopping inducer adjacent any one fioor are selectivelyenergized in accordance with the position of the shields, convenientlyby means of cam-operated switches. associated with the shields.

Preferably the two rotating shields are on the same shaft and arrangedso that the shielding between the primary and secondary members of thetransformer is never complete so that the aforesaid minimum speed isobtained at starting and also just previously to stopp by means of theaction of the stopping controlling electromagnets. The deceleratingshield will usually be designed so as'to provide greater shielding thandoes the accelerating shield. It has been found that the resultantinduced voltage in the sec ondary, which is conveniently common to twoprimaries, when both primaries are energized does not differ appreciablyfrom the voltage induced by the separately connected primary whichis-the les's shielded. Provision may be also made for automaticallyconnecting a resistance in the circuit of the shield motor duringdeceleration so as to cause the motor then to run at a lower speed thanduring acceleration.

The invention above set forth, at least in the preferred form described,provides an electric lift control system having desirablecharacteristics permitting smooth and economical service and involvingin particular complete or substantially complete dynamic control ofacceleration and deceleration. The invention permitsthe attainment ofthe maximum permissible speed between any two floors or landings, theautomatic initiation of deceleration at the latest possible moment onapproaching a floor or landing, and the automatic stopping of the liftor hoist substantially exactly at the fioor or landing level without anycreep or the necessity for re-levelling, and independently of the load.

To enable the invention to be more fully understood and carried intoeffect reference will now be made to the accompanying drawings, whichillustrate embodiments of the invention by way of example.

In the drawings Fig. 1 illustrates in section a controlling transformerand co-operating mag-- netizable member or shield constructed andarranged according to the invention.

Fig. 2 is an elevational view to a reduced scale of the transformer andthe co-operating magnetizable member, illustrating the specific profileof said magnetizable member.

Fig. 3 is a schematic diagram illustrating a system suitable for thecontrol of an electrically operated lift, arranged according to theinvention.

Fig. 4 is an elevational view of a manually adjustable magnetizablemember for co-operating with a transformer such as is illustrated inFig. 1.

Fig. 5 is a schematic diagram of a modified and preferred lift controlsystem in accordance with the invention.

Fig. 6 is a sectional view of a controlling transformer and profiledshield used in the system illustrated by Fig. 5.

'7 is a view illustrating the profiled shields shown in Fig. 6, and

Fig. 8 is the grid volts-output current characteristic of the amplifierwhich feeds the field of the pilot generator as shown in Fig. 5, suchcharacteristic being modified by the inclusion of the armature of thepilot generator in the anode circuit.

Referring to the drawings, in Fig. 1 is shown the E-shaped magnetic coremembers 1 and 2 of the transformer which is designated generally at 3.The cores 1 and 2 are mounted on a non magnetic base 4 with an air gap 5defined by their pole pieces. The core 1 is equipped with the primarywinding 6 and the core 2 with the secondary winding '7. At 8 is shownone form of the profiled shield which is adapted to register with theair gap 5 and to extend thereinto by varying amounts. The shield 8 isdoubly inclined as shown in Fig. 2 and is formed, intermediate its ends,along the forward edge which projects into the air gap 5, with arectangular projection or hump 9. In Fig. 2 the broken lines, indicatethe path along which the air gap 5, as defined by the pole pieces of thecores 1 and 2 of the transformer 3, moves relatively to the shield 8.The transformer 3 is adapted to be secured on a lift car and the shield8 is adapted to be secured in the lift shaft in appropriate position inrelation to a floor or landing.

Referring to Fig. 3 the transformer primary' secondary winding of whichin series with adjustable resistance'll is connected in the input orgrid circuit of a thermionic amplifier valve 12. The output or anodecircuit of the valve 12 includes the primary winding of a transformer 13the secondary winding of which is connected in the grid circuit of asecond amplifying valve 14. The output or anode circuit of the valve 14includes the field winding 15 of the electric generator the armature 16of which is adapted to be connected by leads 1'7 and 18 to the armatureof the motor (not shown) for hauling the lift or to the field winding ofthe main generator supplying that motor. The field winding 15 is shuntedby a condenser 19 of a few microfarads capacity.

In the example being described the grid of the amplifier valve 14 isconnected through a grid condenser 20 to the grid of a third amplifiervalve 21 the output or anode circuit of which includes a contactorswitch operating coil 22 having associated contactor contacts 23 whichare adapted to control the stopping gear (not shown) of the lift. Thisthird valve 21 is normally biased at zero or positive potential so as tooperate on the reduced negative half cycles of the electromotive forceinduced in the secondary 7 of the transformer. Under normal conditions,that is during operation of the lift, the current through the contactoroperating coil 22 will be at a minimum so that the contactor switch 22will be in the open position. When the travel of the lift is such as tobring the transformer air gap into register with the aforesaidprojection 9 of the shield 8, the induced electromotive force will besuddenly reduced so that the current through the contactor operatingcoil will increase suddenly thereby to operate the contactor switch forstopping the lift. The output circuit of the valve 21 also includes theelectromagnetic operating coil 24 for releasing the auxiliarycontroldevice described hereinafter.

The cathodes of the valves 12, 14 and 21 are energized from a source Aof current of ordinary commercial supply frequency, through the trans-'former 25 the legs of the cathode being shunted by a suitable resistance26. The transformer 25 is equipped with a tertiary winding which isconnected through a suitable rectifier 27 and choke 28 associated with ablocking condenser 29 across the outer terminals of the resistancepotentiometer 30 which is provided with tapping points whereby the gridsof the amplifying valves 12, 14 and 21 are maintained at appropriatebiasing potential. The lead from the potentiometer 30 to the grid of thevalve 21 includes a suitable grid leak 31. As hereinbefore mentioned thevalves 12 and 14 are normally biased at zero or negative potential whilethe valve 21 is normally biased at zero or positive potential. Theanodes of the valves 12, 14 and 21 are supplied from a high tensionsource which is indicated at 32, through a smoothing condenser 33.

With the arrangement so far described, with reference to Fig. 3, thestarting operation can be effected by bodily shifting either thetransformer, or the shield or both, in such manner that the amount ofthe magnetizable member extending into the air gap is temporarilyconsiderably reduced and a correspondingly large current is temporarilycaused to flow in the controlled field winding in the mannerhereinbefore described.

Alternatively, the same effect may be obtained by temporarily varyingthe grid bias of one or other of the amplifying valves connected betweenthe transformer and the field winding, such variation being effected,for example, through the intermediary of one or morepush buttonssuitably mounted, say, on the lift and connected'in the grid circuit ofthe valve.

As another alternative, the starting operation can be effected throughthe intermediary of an auxiliary controlling device, comprising atransformer and a co-operating shield similar to the main controllingdevice. In this case both the auxiliary transformer and the shield aresuitably positioned on the lift, the former being also connected to theamplifier, and the shield being mounted so as to be manually movableinto and out of the air gap. A disadvantage of this arrangement is that,when the magnetizable members for the main and auxiliary control devicesare conditioned so as to extend fully into their respective air gaps,the voltage applied to the input side of the amplifier will be doublethat applied when only the magnetizable member for one or other of saidcontrol devices is so condiifioned. This disadvantage however is readilyobviated by the provision of loading means in the circuit of one orother of the control transformers whereby a phase displacement in thevoltages applied to the amplifier bythe respective transformers may beproduced.

The auxiliary device for controlling the starting of the lift is shownin Fig. 3 and comprises a transformer similar to the transformer 3,having a primary winding and a secondary winding 36. The magnetizablemember for the auxiliary control device is indicated at 37 having asuitable handle 38 whereby said member may be moved relatively to thewindings 35 and 36. The form of the magnetizable member 37 isillustrated more particularly in Fig. 4, the broken lines in this figureindicating the position which is normal 1y occupied by the pole piecesof the transformer.

The primary winding 35 is supplied from the nected to the primarywinding of the step-up transformer 39 the secondary winding of which,inserieswithanadjustableresistancewJccm nected'in parallel with thesecondary winding ofthestep-uptransformer loanditsseriesresistance 11 inthe input circuit of the valve 12. The resistance 40 affords means forvarying the phase relationship between the currents induced in thesecondary windings of the transformers 10 and 39 respectively while theresistance 11 may be utilized to vary the rate of acceleration anddeceleration.

It will be appreciated that where the auxiliary controlling device isemployed in a lift system it vmay, in addition to being arranged forcontrolling the fleld winding of the hauling motor, generator, orexciter therefor, be utilized to govern the operation of the up" and"down direction switches which are usually to be found in a lift systemfor determining the direction of operation of the lift.

Where both main and auxiliary controlling devices as described areemployed, it is desirable, 100 in certain circumstances, that only oneor other of said devices should be rendered operative at any particularinstant. For example, in the case of the lift system, when automaticdeceleration of the lift is being effected by the pro- 108 gressiveintroduction of the shield for the main transformer into the air gap, itwould be very undesirable if the decelerating operation could beinterfered with by manipulation of the auxiliary controlling device.Such interference may 110 be prevented by suitably interlocking the mainand auxiliary controlling devices. In one form, the auxiliarycontrolling device may be provided with retaining means (not shown)which is normally operative, when the lift is in motion, to 116 preventrelative movement of the auxiliary transformer and its co-operatingshield and is only released when the lift has been brought to rest. Thusthe retaining means may be provided with a releasing electromagnet whichis In energized, when the current in the operating coil 24 attains avalue sufficient to cause the operation of the stopping contactor 22,23, so as to condition the auxiliary controlling device either at thesame time as, or at the end of a suitable 128 interval of time after,the operation of said stopping contactor 22, 23.

Referring now to Figs. 5 to 8, inclusive of the accompanying drawings bywhich the preferred arrangement of the invention is illustrated, in Fig.5 is shown schematically a lift control system embodying the invention.A hauling motor 43 for raising and lowering a lift car (not shown) in ausual manner is supplied by the Ward- Leonard generator 44 the fieldwinding 45 of which is excited by the pilot generator 46 driven atconstant speed by a motor 47 adapted to be connected by a switch 48 todirect current supply mains 49 or other convenient source of suitablevoltage, such as a generator which supplies brakes and other controlgear. A controller 42 may be mounted on the car for controlling thestarting and stopping of the car.

The armature 50 of the pilot generator 46 is serially connected with itsfield winding 51 (bridged by a condenser 52) between the positive supplymain (through a switch 53) and the anode of the output valve 54 of theamplifier 55 so that the voltage generated by the pilot gen- 1 erator isadded to the potential of the supply mains giving the valve 54 anoperating characteristic such as shown by way of example in F18. 8, withthe effect hereinbefore set forth. The valve is suitably negativelybiased and the apparent resultant voltage characteristic may be as shownat 56 in Fig. 8.

An up direction switch U and a down direction switch D operated by thecontroller 42 are provided for controlling the direction of operation ofthe pilot generator 46 and consequently the direction of operation ofthe car. A starting relay S is also provided for preparing the controlcircuits for operation.

Referring again to Fig. 5, the pilot generator 46 also has a smallassisting series winding connected across a resistive shunt 58 in themain motor circuit, with the effects hereinbefore set forth.

The grid of the output valve 54 is supplied during certain times with analternating voltage from a preceding or input amplifier stage valve 59the grid of which is excited by means of the controlling transformer 60which is shown separately in Fig. 6. Said transformer 60 has thesecondary winding 61 and the two primary windings 62 and 63 adapted tobe connected by switches 64 and 65 respectively to a source ofalternating current of ordinary commercial frequency represented by thesupply mains 66. The windings of the transformer 60 are mounted onseparate respective cores 67, 68 and 69 (Fig. 6) secured to thenon-magnetic base board 70, with air gaps between the cooperating coreswith which cooperate the two magnetic disc shields 71 and 72 (Fig. 7)mounted on the shaft 73.

The switch 64 is controlled by a high speed relay HS and the switch 65by the starting relay S.

The shaft 73 (Fig. 5) is rotated, preferably through reduction gearing(not shown) by the constant speed motor '14 having a shunt field winding75 and adapted to be connected to the supply mains 49 through twoswitches 76 and '17 whilst the armature of said shield motor '74 isadapted to be reversely connected by coupled pairs of reversing switches'78 and 79 of which 79 are normally closed. The operation of the switch77 is controlled in part by means of a cam 80 secured in proper timingposition on the shaft '73 of the shield motor 74.

The operation of the reversing switches 78-79 is controlled by areversing relay M, which relay also holds the high speed.

Considering only the upward travel of the lift, there are providedadjacent each floor and in vertical alignment the three controllingelectromagnets or inducers 83, 84 and 85 the windings of which areconnected on the one hand by a switch 86, controlled by an inducer relayI to one of the A. C. mains 66 and on the other hand to the other ofsaid mains 66 through respective switches 8'1, 88 and 89. The operationof the switches 8'7 and 88 is controlled in part by respective cams 90and 91 on the shaft 73 of the sheld motor 74 whilst the switch 89 iscontrolled by the starting relay S. The inducers 83 and 85 are energizedwhen stopping from high speed and the inducers 84 and 85 when stoppingfrom a short or low speed run. v

Fixed on the lift (not shown) so as to be successively excited by theinducers 83 and 85 or 84 and 85 is the pick up winding 92 which isconnected by a pair of conductors in a trailing cable 93 through a wire95 with the input grid of the pulse amplifier 96.

The output valve 97 ofthe amplifier 96 has in its anode circuit a coilor pulse relay 98 operating a contactor switch 99 which by successiveoperations and through the medium of a system of sequence switches orequivalent interlocks effects the different operations as hereinafterdescribed.

A description of the operation of the system shown in Fig. 5 inconjunction with further description of that figure will now be given.

The controller 42 has an off" position and two notches or positions oneither side thereof for upward and downward travel of the lift, thefirst notch a or b causing the lift to travel at the minimum slow speedand the second notch c or d causing the lift to be acceleratedautomatically towards the maximum speed. The arrangement is such that,when the controller is re turned to the "off" position, decelerationwill be automatically effected to bring the lift to rest at the nextfloor in the direction of travel, it being necessary in order to passfloors to hold the controller in one of its operative positions ornotches.

Assuming now that the controller is moved in 100 a clockwise directionto the first or slow speed notch for upward travel of the car, then thecontact members a and e of the controller will close to energize thestarting relay S, the up direction relay U, and the inducer relay I.

The energization of the starting relay S closes its switches 84, 53, 101and energizes the relay SA for closing switch 108 to energize theappropriate control circuits and start the motor generator set 47, 46.

The energization of the up direction relay U closes its contact membersa and b for operating the pilot generator 46 in the up direction andcloses its contact members 0 for preparing a circuit for connecting theup decelerating inducers 83, 84 and 85 when the car is to be stopped onits up trip. The closing of the contact members d of relay U completes aself-holding circuit for relays U and S whereby these relays aremaintained energized during deceleration of the car to a stop by theinducers 83, 84 and 85 until the final stopping operation is completed.

The energization of the inducer relay I opens the switch 86 and therebyprevents operation of the inducers 83, 84 and 85 to stop the car untilafter the controller 42 is moved to its ofl position for a stop.

Whenever the car is at rest at a floor or landing, the shields '71 and'72 provide a maximum but incomplete shielding between the primary 0'windings 62 and 63 on the one hand and the secondary winding 61 on theother hand of the transformer 60, so that a small current flows in theanode circuit of the valve 54 by reason of the switch 65 of the-primarywinding 63 being 136 closed due to the energization of the startingrelay S. If the controller is held in the first notch, the lift willcontinue to travel at the aforesaid minimum slow speed, but if now thecontroller is moved to the second notch, the contact members I and d ofthe. controller close thereby energizing the high speed relay HS tocause the car to accelerate to high speed.

The energization of the high speed relay HS 1 closes switches 64, '76,201, and 203. Closing the switch 203 completes a self-holding circuitfor the high speed relay HS. The opening of the switch 202 preventsenergization of the relay K until the car is again brought to a stop.The closing of w the relay Q to be used later in stopping the car. I

The closing of the switch 64 connects the primary 62 of the transformerto the supply line 68 and the closing of the switch 76 completes acircuit for operating the shield motor 74. Thereupon the shield motor iscaused to rotate atconstant speed in the accelerating direction, so thatthe car will be accelerated at the predetermined maximum rate by reasonof the movement of the shields 71 and 72 through the air gaps betweenthe primary windings 82 and 63 and the secondary winding 61 of thetransformer 60, thus controlling the circuit to the amplifier 55. Whenthe shield motor '74 reaches a predetermined position, the cam 80 opensthe switch '17 thereby stopping the motor and causing the car tocontinue to run at its maximum speed so long as the controller 42 isheld in the second notch position.

Assuming now that it is desired to bring the car to a stop at the fioorcorresponding to the inducers 83, 84 and 85, the controller 42 isreturned to its 0 position while the car is more than the predetermineddecelerating and stopping distance from the floor. Upon the centering ofthe controller, the inducer relay I is deenergized to close its switch86, which closing completes a circuit energizing the inducers 83 and todecelerate and stop the car when the pick-up coil 92 passes them. (Theinducer 84 is not energized because cam switch 87 remains open by reasonof the position of the shield motor, inasmuch as the stop is to be madefrom high speed and not from intermediate speed.)

It should also be noted although the controller 42 is now in its 0position; the up direction relay U, the starting relay S and the highspeed relay HS still remain energized because of their holding circuitsand will now be deenergized in sequence as the car passes the inducers83 and 85 to decelerate and stop the car level with the fioor.

Hence, when the lift car, travelling at full speed, is at a certaindistance from the selected floor, at which it is to stop, the pick-upwinding 92 on the car passes the now energized inducer coil 83 and isexcited thereby. The excitation of the coil 92 operates through theamplifier 96 to energize the pulse relay 98 to close the switch 99 toeffect deceleration of the car. The closing of the switch 99 energizesthe relay Q to open its contact members 204 and also energizes the relayM to open the switch 205. The opening of the switch 205 opens theself-holding circuit of the high speed relay, thereby deenergizing thatrelay to open switch 64 to deenergize the primary coil 62 and to openswitch 76 leading to the shield motor 74.

The energization of the relay M opens the reversing switches 79 andcloses the reversing switches 78, thereby causing the motor 77 to startrotating in the reverse direction. The opening of the switch 64 resultsin an initial drop in volts induced in the secondary winding 81 of thecontrolling transformer 60.

The shields 71 and 72 are now gradually entered into the transformer airgaps by the rotation of shaft 73 effected by the reverse operation ofthe shield motor '74 so that the lift is automatically decelerated atthe predetermined rate to the minimum slow speed prior to the carreaching the floor landing level.

Just before the car reaches the landing floor level, the pick-up winding92 comes adjacent to the p inducer 85 and is thereby energized to theswitch 201 prepares a circuit for energizing operate the pulse relay 98a second time to effect the stopping of the car.

The energization of the pulse relay 98 closes its contact members 99,thereby energizing the relay K to close its contact members a and openits contact members b. The closing of the contact members a of relay Kcompletes a selfholding circuit for that relay and the opening of itscontact members I) deenergizes the up-direction relay U and the stoppingrelay 8, which deenergized relays open the circuits for the generator 46and the control circuits, thereby bringing the car to a stop.

The deenergization of the starting relay also opens the switch 207,thereby opening the selfholding circuit of the relay K to prepare thatrelay for future operation, and also opens the self holding circuit ofthe relay M to prepare a reversing circuit for operating the shieldmotor 74 in the accelerating direction when the car is to 98 be againaccelerated.

Inthecasewheretheliftisrequiredonlyto travel from one fioor to the nextso that full speed cannot be attained, the lift is started by moving thecontroller 42 to the second notch and the controller is then returned tothe oil'" position whereupon the aforesaid holding or maintainingcircuits and switches and additional interlocks cause the inducers 84and 85 (and not the inducer 83) to be connected to the supply main 66through the switch 8'7 under the control of the cam which becomeseffective whenever the shields l1 and '72 have moved out of the normallyfullyinposition. Thus no matter what may be the speed of the lift underthese conditions the excitation of the pick-up winding 92 by the inducer84 (medium inducer) and then by the stop inducer 85 will cause twosuccessive operations of the pulse relay 98 which thus results in themotor '74 being reversed immediately deceleration is required so thatthe lift is decelerated at the predetermined maximum rate, andeventually brought to rat in the manner previously described.

Referring finally to Fig. 7 of the drawings. it m will be appreciatedthat the nature of the acceleration and deceleration is governed by theprofile of the shields '11 and '72 such as shown in that figure and bythe speed of rotation of said shields. The shape can easily bedetermined by 13 experiment to suit any given site conditions. The shapeof the shields is of course dependent upon the time constant of thegenerator field but the shields are in full control of that field, thusavoiding the necessity for large time constants. m The shields may be ofordinary spiral shape as shown in Fig. '7, each with end portions ofconstant radius between the dotted radii shown. The decelerating shield72 is preferably larger than the accelerating shield 71, as shown inP18. '7.

It will be appreciated that in either of the systems shown, if a valveof an amplifier fails, the lift will be automatically brought to rest.In order to protect against failure of the grid bias- 0 ing potential onany of the valves in the system, high resistance relays may be employedarranged to cut off for example the cathode supply current so that thewhole system becomes de-energized and the lift stops until the gridbiasing potential is restored.

It will be further appreciated that the pulse amplifier 96 can beomitted if the alternating current induced in the pickup windings issufiiciently strong to operate, after being passed through a Illrectifier, the pulse relay 98. Ordinarily the induced currents will becomparatively weak so as to necessitate amplification and this it -willbe appreciated is an important advantage of the system which it will befurther appreciated obviates mechanical contact between the movin liftand the fixed devices; no switches, other than those of the controller,are provided on the car or in the shaft; the automatic control isobtained by inductive and leakage operation with devices energized bylow frequencyaltemating current of relatively low voltage and currentstrength; the inductive apparatus need only be small and relativelyinexpensive, and relatively large air gaps can be employed.

It is to be understood that various further modifications and additionsmay be'made within the scope of the invention. For example the manualcontroller may be replaced by press-button control. The shield orshields may be retated from any convenient rotating member through theintermediary of one or more clutches adapted to be operated atappropriate times; thus the accelerating shield 71 may be clutched tothe shaft of the motor generator set 47, 46 whilst the deceleratingshield '72 may be clutched to the pulley shaft of the main hauling motor43; the shield motor may be provided with a small adjustable seriesfield excited in accordance with the main motor current so as to adjustthe speed of deceleration with load whereby to produce the requiredlanding speed.

In the appended claims the expressions control systems and controlapparatus are intended to embrace signalling systems or apparatusalternatively or in addition to control systems or apparatus such as forthe motors or auxiliary equipment of lifts, elevators, railway cars andthe like.

I claim as my invention:

1. In a motor-control system of the class in which a separately excitedmotor is supplied by means of a separately excited variable voltagegenerator, a vacuum tube having output electrodes and a control element,means responsive to the current of said output electrodes for varying acomponent of excitation of said generator, an alternating-currentsource, and means interconnecting said source and said control elementincluding a variable mutual inductance device having a movable elementfor gradually varying the voltage applied to said control element,whereby said component of excitation of said generator may be varieduniformly throughout a predetermined range of values.

2. In a motor-control system of the class in which a separately excitedmotor is supplied by means of a separately excited variable-voltagegenerator, means responsive to the armature current of said motor forvarying a component of excitation of said generator to correct the speedregulation of said motor, a vacuum tube having output electrodes and acontrol element, means responsive to the current of said outputelectrodes for varying a second component of excitation of saidgenerator to vary she speed of said motor, an alternating-currentsource, and means interconnecting said source and said control elementincluding a variable mutual inductance dewhich a separately excitedmotor is supplied by means of a separately excited variable-voltagegenerator, an exciter for varying a component of excitation of saidgenerator, a source, a vacuum tube having outputelectrodes energized inaccordance with the voltage of said source and the armature voltage ofsaid exciter for controlling a component of excitation of said exciter,said vacuum tube having a control element, and means for variablyenergizing said control element to thereby vary the speed of said motor.

4. In a motor-control system of the class in which a separately excitedmotor is supplied by means of a separately excited variable-voltagegenerator, an exciier for varying a component of excitation of saidgenerator, a source, a vacuum tube having output electrodes energized inaccordance with the voltage of said source and the armature voltage ofsaid exciter for controlling a component of excitation of said exciter,said vacuum tube having a control element, means responsive to thearmature current of said motor for controlling a second component ofexcitation of said exciter to correct the speed regulation of saidmotor, and means for variably energizing said control element to therebyvary the speed of said motor.

5. In a motor-control system of the class in which a separately excitedmotor is supplied by means of a separaiely excited variable-voltagegenerator, an exciter for controlling a component of excitation of saidgenerator, a source, a vacuum tube having output electrodes energized inaccordance with the voltage of said source and the armature voltage ofsaid exciter for controlling a component of excitation of said exciter,said vacuum tube having a control element, an alternating-currentsource, and means including a variable mutual inductance deviceinterconnecting said alternating-current source and said controlelement, for varying the speed of said motor.

6. In a motor-control system of the class in which a separately excitedmotor is supplied by means of a separately excited variable-voltagegenerator, an exciter for controlling a component of excitation of saidgenerator, a source, a vacuum tube having output electrodes energized inaccordance with the voltage of said source and the armature voltage ofsaid exciter for controlling a component of excitation of said exciter,said vacuum tube having a control element, means responsive to thearmature current of said motor for varying a second component ofexcitation of said exciter to correct the speed regulation of saidmotor, an alternating-current source, and means including a variablemutual inductance device interconnecting said alternating-current sourceand said control element for varying the speed of said motor.

'7. In a control system, an exciter, a source, a vacuum tube havingoutput electrodes energized in accordance with the voltage of saidsource and the armature voltage of said exciter for controlling acomponent of excitation of said exciter, said vacuum tube having acontrol element, a main dynamo-electric machine having a field windingresponsive to the armature voltage of said exciter and means forvariably energizing said control element to thereby vary the excitationof said main dynamo-electric machine.

8. In an elevator system, an elevator car operable in a hatchway, amotor for driving said car, a variable-voltage generator for supplyingsaid motor, an inductance device having a pair of mutually inductivecircuits and having a movable magnetic member for varying the mutualinductance of said circuits, means for energizing one of said circuitswith alternating-current, an electric discharge device having electrodesenergized in accordance with the voltage induced in the other of saidcircuits, means responsive to the discharge current of said device forcontrolling a component of excitation of said generator, and means forvarying the position of said magnetic member to thereby control thespeed of said motor.

9. In an elevator system, an elevator car operable in a hatchway, amotor for driving said car, a variable-voltage generator for supplyingsaid motor, an inductance device having a pair of mutually inductivecircuits and having a movable magnetic member for varying the mutualinductance of said circuits, driving means for said magnetic member,means for energizing one of said circuits with alternating-current, anelectric discharge device having electrodes energized in accordance withthe voltage induced in the other of said circuits, means responsive tothe discharge current of said device for controlling a component ofexcitation of said generator, and means responsive to the position ofsaid car for controlling the operation 01' said driving means.

10. In an elevator system, an elevator car 0perable in a hatchway past alanding, a motor for driving said car, a variable-voltage generator forsupplying said motor, an inductance device having a pair of mutuallyinductive circuits and having a movable magnetic member for varying themutual inductance of said circuits, driving means for said magneticmember, means for enamass ergizing one of said circuits withalternatingcurrent, an electric discharge device having electrodesenergized in accordance with the voltage induced in the other 01 saidcircuits, means responsive to the discharge current '01 said device forcontrolling a component of excitation 01' said generator, meansresponsive to the armature current of said motor for controlling asecond component of excitation of said generator to correct the speedregulation 01 said motor and means responsive to the position 01' saidcar for controlling said driving means to decelerate said car in advanceof said landing and to bring said car to rest at said landing.

11. In an elevator system, an elevator car operable in a hatchway past alanding, a motor for driving said car, a variable-voltage generator forsupplying said motor, an alternating-current source, an electricdischarge device, means including a variable mutual inductance deviceinterconnecting said source and said discharge device ior controllingthe discharge current of said dischargedevic'e, means responsive to thedischarge current of said device for controlling a component ofexcitation of said generator, means responsive-to the armature currentof said motor for controlling a second component of excitation of saidgenerator to correct the speed regulation of said motor, a pick-up coilmounted on said car, means for establishing an alternating field atpredetermined points in said hatchway to influence said pick-up coil,and means responsive to currents induced in said pick-up coil forcontrolling said variable mutual inductance device.

RONALD JOHIN SI'EVENS.

